Department of Thoracic Medicine and Surgery, Lewis Katz School of Medicine at Temple University, Philadelphia, PA (Drs. Parth M. Rali and Gupta); Family Medicine, Northwell Health, NY (Dr. Baffour-Awuah); Children’s Hospital of Philadelphia, PA (Dr. Grishma Rali); Department of Family Medicine, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY (Dr. Mayur Rali) mrali@northwell.edu
The authors reported no potential conflict of interest relevant to this article.
It’s an exciting era of asthma management, with the introduction of several novel modalities, including biological therapy and bronchial thermoplasty.
Recent advances in our understanding of asthma pathophysiology have led to the development of new treatment approaches to this chronic respiratory condition, which affects 25 million Americans or nearly 8% of the population.1 As a result, asthma treatment options have expanded from just simple inhalers and corticosteroids to include biological therapies, immunotherapy, bronchial thermoplasty, and anti-inflammatory agents. This review will focus on the newer therapeutic options and provide guidance on when to seek expert pulmonary consultation (TABLE 1). But before we begin, it’s important to briefly review the pathophysiology of asthma and several key diagnostic considerations.
The pathophysiology of asthma provides key targets for therapy
There are 2 basic phenotypes of asthma—neutrophilic predominant and eosinophilic predominant—and 3 key components to its pathophysiology2:
Airway inflammation.Asthma is mediated through either a type 1 T-helper (Th-1) cell or a type 2 T-helper (Th-2) cell response, the pathways of which have a fair amount of overlap (FIGURE). In the neutrophilic-predominant phenotype, irritants, pollutants, and viruses trigger an innate Th-1 cell–mediated pathway that leads to subsequent neutrophil release. This asthma phenotype responds poorly to standard asthma therapy.2-4
In the eosinophilic-predominant phenotype, environmental allergic antigens induce a Th-2 cell–mediated response in the airways of patients with asthma.5-7 This creates a downstream effect on the release of interleukins (IL) including IL-4, IL-5, and IL-13. IL-4 triggers immunoglobulin (Ig) E release, which subsequently induces mast cells to release inflammatory cytokines, while IL-5 and IL-13 are responsible for eosinophilic response.These cytokines and eosinophils induce airway hyperresponsiveness, remodeling, and mucus production. Through repeated exposure, chronic inflammation develops and subsequently causes structural changes related to increased smooth muscle mass, goblet cell hyperplasia, and thickening of lamina reticularis.8,9 Understanding of this pathobiological pathway has led to the development of anti-IgE and anti-IL-5 drugs (to be discussed shortly).
It is important to determine whether patients with asthma-COPD overlap syndrome are asthma predominant or COPD predominant, because appropriate first-line treatment will differ.
Airway obstruction.Early asthmatic response is due to acute bronchoconstriction secondary to IgE; this is followed by airway edema occurring 6 to 24 hours after an acute event (called late asthmatic response). The obstruction is worsened by an overproduction of mucus, which may take weeks to resolve.10 Longstanding inflammation can lead to structural changes and reduced airflow reversibility.
Bronchial hyperresponsiveness is induced by various forms of allergens, pollutants, or viral upper respiratory infections. Sympathetic control in the airway is mediated via beta-2 adrenoceptors expressed on airway smooth muscle, which are responsible for the effect of bronchodilation in response to albuterol.11,12 Cholinergic pathways may further contribute to bronchial hyperresponsiveness and form the basis for the efficacy of anticholinergic therapy.12,13
What we’ve learned about asthma can inform treatment decisions
Presentation may vary, as asthma has many forms including cough-variant asthma and exercise-induced asthma. Airflow limitation is typically identified through spirometry and characterized by reduced (< 70% in adults) forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) or bronchodilator response positivity (an increase in post-bronchodilator FEV1 > 12% or FVC > 200 mL from baseline).2 If spirometry is not diagnostic but suspicion for asthma remains, bronchial provocation testing or exercise challenge testing may be needed.
Continue to: Additional diagnostic considerations...